The long-range goal of this research is a better understanding of the basic mechanism and regulation of iron metabolism, which would, in turn, lead to a better understanding of metabolic disorders, such as iron deficiency anemia or abnormal increase of body iron known as hemochromatosis. In particular, this research would attempt to assess the importance of a newly discovered intestinal enzyme system, which promotes the oxidation of iron and its incorporation into transferrin, in the mechanism and regulation of dietary iron absorption. Since changes in the iron content of diet of laboratory rats leads to rapid changes in the amount of iron absorbed by the intestinal mucosa, laboratory rats maintained on diets of various iron content provide a convenient system for evaluating the physiological significance of this intestinal enzyme. The activity attributable to this enzyme will be analyzed in mucosa from iron-deficient, iron-loaded, copper-deficient, and control animals. Variations in the amount or activity of this enzyme could control the fraction of total mucosal iron which becomes incorporated into transferrin and enters the blood stream. The intestinal enzyme system has been partially purified by gel filtration and ion-exchange chromatography. A chemical and kinetic characterization of the purified enzyme will also be performed. The properties of this intestinal enzyme which promotes Fe(III)-transferrin formation will be compared to those of the blood serum ferroxidases which function in a similar capacity in iron mobilization but have been shown not to participate in dietary iron absorption.